The present invention pertains to a process for the manufacture of MgCl.sub.2.MgO with narrow granulometric distribution by treatment of hydrated MgCl.sub.2 in an alcohol. The treatment induces the granulometric rearrangement of the particles of the initial hydrated MgCl.sub.2. The most noteworthy phenomena occurring during the granulometric rearrangement are the disappearance of the fine particles and the disappearance of the large particles of the initial hydrated MgCl.sub.2 with the appearance of particles whose granulometric distribution is narrow.
The resultant MgCl.sub.2.MgO can be employed as a catalytic support, especially in catalytic components of the Ziegler-Natta type. These catalytic components used in the polymerization of olefins have the advantage of producing polymers with a narrow particle-size distribution, for which reason such polymers have excellent application qualities.
Treatment of MgCl.sub.2.MgO supports in the presence of hydroxylated compounds is known, e.g., from GB 1,559,172, but all of these known cases solely involve forming complexes with hydroxyl functions, without concern for the granulometric distribution of the final product. In accordance with all of these treatments, the final complex remains essentially identical to the initial MgCl.sub.2.MgO with its fine and large particles.